The self-driving industry’s Wild West days are done. An elite group of giants has taken the lead, and any challengers are likely doomed.

The top tier includes Waymo, Cruise, Argo AI, Aurora, and Motional. According to Pitchbook, there were a total of 33 mergers and acquisitions involving autonomous-vehicle companies in 2019 and 2020, compared to 22 such deals between 2017 and 2018. Experts typically rank a similar handful of companies just below Waymo, including Cruise, Argo AI, Aurora, and Motional. Reilly Brennan, a general partner at the venture-capital firm Trucks, wrote in a May newsletter that new autonomous-vehicle startups are looking beyond ride-hailing. Nuro has illustrated the enthusiasm that autonomous-vehicle startups can generate by moving goods instead of people.